This invention relates to known devices for liquefying gases condensing at very low temperature, such as helium, hydrogen and neon, such devices including an inlet duct for high-pressure gas incorporating one or more pre-cooling devices and one or more counter-flow heat-exchangers, in which a high-pressure gas cools down below its inversion temperature associated with said pressure, also included is an outlet communicating with a pressure-reduction device, the outlet thereof opening into a collecting container for condensed gas comprising a vapour space having an outlet duct for low-pressure gas incorporating the counter-flow heat-exchanger (exchangers).
The high-pressure gas which is pre-cooled below the associated inversion temperature is throttled to a substantially lower pressure in the pressure-reduction device, its temperature then decreasing because of isenthalpic expansion (Joule-Kelvin effect). Because the values of the temperature and the pressure after departure from the pressure-reduction device are below the critical temperature and pressure values, at least part of the gas has been liquefied. The condensed gas flows into the collecting container. The expanded and non-condensed gas is normally returned, via counter-flow heat-exchangers, to the suction side of a compression installation which supplies the high-pressure gas.
Dewar vessels filled with liquid nitrogen, neon, hydrogen or even helium, for example, are used as the cooling device for pre-cooling the gas under high pressure. Use is sometimes also made of expansion machines in which a branched-off part of the high-pressure gas flow expands while performing mechanical work, cold thus being developed by which the high-pressure gas flow is pre-cooled.
Refrigerators are also often used for precooling, notably cold-gas refrigerators. For example, the article "A gas refrigerating machine for temperatures down to 20.degree. K and lower" (Philips Technical Review, Volume 26, 1965, No. 1) describes helium liquefactor (FIG. 12) in which the high-pressure helium is pre-cooled in two stages (to approximately 80.degree. K and approximately 15.degree. K) by means of a three-space cold-gas refrigerator.
As is known in practice, not only liquefaction of gases such as helium, hydrogen and neon occurs, but the constituents of gas mixtures such as helium-neon mixtures also may have to be separated; this is normally effected in typical gas separation installations.
The invention has for its object to provide an improved device of the kind set forth by a structurally simple extension of the known device, so that not only single gases can be liquefied, but that also gas mixtures can be separated into the individual constituents.